SOL-GEL PRECURSOR FOR ALUMINA SILICON-CARBIDE NANOCOMPOSITE THROUGH CONTROLLED FLOCCULATION AND HUMIDITY DRYING

An alumina-silicon carbide nanocomposite precursor was prepared by a s ol-gel method using a boehmite sol and a kinetically stable colloidal suspension of ultrafine (<0.3 mu m) silicon carbide particles. Floccul ation of the boehmite sol containing uniformly dispersed silicon carbi de particles using ammonia immobilised the dispersed particles resulti ng in uniform drying and shrinkage. Drying under controlled humidity c onditions of 45 degrees C and 60-70% relative humidity, produced crack free green precursor bodies which retained their shape after heat tre atment at 1450 degrees C.